The invention relates to an occupant restraint system of a vehicle in accordance with the preamble of claim 1. Furthermore, the invention relates to an occupant restraint system comprising such airbag package as well as a method of manufacturing an airbag package. An airbag package of the type mentioned in the beginning is known, for example, from EP 1 127 752 A2.
In general, airbag packages are formed of a folded airbag which is usually made of textile fabric. Between the folds of the airbag and the individual fabric threads, viz. the material of the airbag, clearances are formed in the airbag package. Concretely speaking, the airbag package thus consists of the folded airbag and a particular air volume enclosed in between the material of the airbag.
For the manufacture of an airbag it is known to initially fold the airbag and then to transfer it into a cover cap. In the cover cap the airbag is fixed so that it can subsequently be inserted into a steering wheel or an instrument panel, for example. The outer shape of the airbag package is not stable, however, but independently falls apart unless it is fixed in the cover cap. The airbag package shows this tendency to unfolding again even after being inserted in the cover cap. Consequently, the airbag package constantly urges against the cover cap during its entire service life. This continuous load is shown in the course of time at the tearing edge of the cover cap and impairs the optical appearance of the cover cap.
Also during manufacture the instability of the airbag package entails problems. In the manufacturing method according to EP 1 127 752 A2 the airbag is folded with the aid of a film enclosing the airbag. Subsequently the airbag package has to be removed from the film and transferred into the cover cap. Although the airbag package is compressed under the influence of temperature so that the folding is retained for a limited period of time, the airbag package nevertheless springs somewhat open so that the actual package volume is considerably larger due to the air enclosed therein than the airbag volume which can be calculated as theoretical airbag volume from the density of the material used for manufacturing the airbag. Also, the shaping is not permanent in the manufacturing method according to EP 1 127 752 A2.